The present invention relates generally to torque oscillation compensation for electric motors, and more particularly, to a torque oscillation compensation system and circuit that senses battery current to generate a compensation signal.
Electric drive train systems can exhibit torque pulsations. These torque pulsations can cause motor bearing and tire wear. The torque pulsations can also cause undesirable drive train/vehicle vibration. Prior art devices for use in stabilizing electric vehicles have attempted to implement vehicle stabilization using gyroscopic compensation. However, gyroscopic techniques have not yet proved to be feasible for use on electric vehicles. Other conventional approaches include in-line torque transducer feedback, DC bus voltage modulation, and external series/parallel element for motor, and the like.
It has also been known for some time that induction motors that are driven by variable frequency controllers exhibit torque fluctuations, especially at low speed. Electric vehicles that are propelled by such induction motors therefore exhibit torque fluctuations. This results in unstable operation at low speed and can affect the marketability of the vehicle. Consequently, the prior art approaches are not cost effective and/or technically suited for use in many electric drive train applications.
Accordingly, it is an objective of the present invention to provide for a torque oscillation compensation circuit that senses battery current to generate a compensation signal to compensate for pulsations experienced at the output shaft of an electric motor.